When a nucleus of neptunium decays, a $\beta$-particle and $\gamma$-radiation are emitted. What change, if any, does this decay cause to the proton number and to the nucleon number of the nucleus?
- Aproton number increases; nucleon number decreases
- Bproton number decreases; nucleon number increases
- Cproton number unchanged; nucleon number decreases
- Dproton number increases; nucleon number unchanged